Figure 2.

All-points amplitude histograms of single-channel currents elicited by solutions of pH_o 6.0, 5.0, and 4.0 recorded from outside-out patches at −80 mV and with 150 mM Na⁺ in the bath and 150 mM K⁺ in the pipet. The distributions were fitted by the sum of two Gaussian components (continuous lines). The mean amplitude of the open state is −1.8 ± 0.01 pA for the three different pH_o solutions. The areas under the curves are as follows: 0.2 and 0.8 at pH_o 6.0; 0.28 and 0.72 at pH_o 5.0; and 0.45 and 0.55 at pH_o 4.0. Since the average P_o at pH_o 6.0 is low, we chose a segment of high activity to obtain a significant number of points on the open state.